Polyester Resin and Method for Preparing the Same

1. A method for preparing polyester resin, comprising the steps of: carrying out an esterification reaction or a trans-esterification reaction of acid components and diol components at the increased pressure of 0.2˜3.0 kg/cm 2 and the temperature of 240˜300° C. during an average retention time of 2˜10 hours; and carrying out a polycondensation reaction for a product of the esterification reaction or the trans-esterification reaction at the reduced pressure of 400˜0.1 mmHg and at the temperature of 240˜300° C. during an average retention time of 1˜10 hours, wherein the acid components comprise terephthalic acid, and the diol components comprise (i) 42˜58 mol % of 1,4-cyclohexanedimethanol and (ii) 19˜40 mol % of isosorbide with respect to the total diol components, and a glass transition temperature (Tg) of the polyester resin is more than 104° C., and notch izod impact strength of the polyester resin is more than 129 J/m.